1. Field of the Invention
The present invention relates to an optical device and a laser microscope.
This application is based on Japanese Patent Application No. 2007-292413, the content of which is incorporated herein by reference.
2. Description of Related Art
In a conventionally known technique, an optical isolator is disposed in the subsequent stage of a laser light source, for preventing the problem of unstable laser oscillation, causing a failure, because of part of the laser light emitted from the laser light source and transmitted to a two-photon excitation microscope is reflected, at a midpoint in the transmission, back to the laser light source (for example, refer to D. L. Wokosin, et al., “Characterization of Range of Fura Dyes with Two-Photon Excitation”, Biophysical Journal, Volume 86, March 2004, p 1726-1738).
However, an optical isolator is not only inefficient, but is also an expensive means for preventing reflected return light occurring when laser light over a wide wavelength range is transmitted. Further, because it is driven by magnetic force, it may create a magnetic field around itself, which exerts a negative influence on the surroundings. In addition, when a femtosecond pulsed laser light source is used as the laser light source, as in a two-photon excitation microscope. Sufficient compensation of the group-velocity delay dispersion needs to be performed, because it of the optical isolator is large.